The present invention relates to an exhaust system of an internal combustion engine, and more particularly an exhaust system of an internal combustion engine especially adapted for use as a power source for a portable tool such as a chain saw.
The muffler of an internal combustion engine of a portable chain saw or the like rises to a high temperature during the operation so that it must be enclosed within a cover in order to prevent an operator from directly touching the muffler and consequently being seriously burned. In addition, an internal-combustion-engine-powered portable machine or tool such as a portable chain saw must be made as light in weight as possible for permitting the easy handling of the portable machine or tool. For this purpose, the muffler, among others, must be made as light in weight as possible, but in order to maintain the safeguarded and pollution-free working conditions, the sound attenuation efficiency as well as the exhaust gas cleaning or exhaust emission control efficiency cannot be sacrificed at all.